1. Field of the Invention
This invention relates to improvements in swab printing machines.
2. Prior Art
By means of the swab printing process, smooth and uneven surfaces of objects can be printed on in a simple manner. After the inking of the printing plate and removal of the excess ink, the printing pillow, also known as a swab, is pressed onto the printing plate, raised therefrom and then pressed against the object to be printed on, in order to transfer the printed image.
A swab printing machine of this type is known in Swiss Pat. No. 546,644. A spreader guide body is attached to the spreader support of this machine, which spreader guide body includes an opening in which the spreader is slidably mounted. A slot is provided in the center of the spreader, in which slot a guide pin engages in order thereby to limit the level of the spreader between two end positions.
The spreader, which is made of sheet steel, is drawn downward by its own weight. In the lower end position the lower edge of the spreader dips a few millimeters deep into the ink container. The dipping depth is determined so that an optimal quantity of ink is transported onto the printing plate.
Too deep of an immersion would have disadvantageous results. On the one hand, too much ink would be pushed onto the printing plate and on the other hand, ink would be sprayed backward during each return and immersion into the ink container.
In order to maintain the optimal dipping depth at a more or less constant level, the ink container must be refilled often. Furthermore, no mixing of the ink takes place, because the spreader always penetrates only into the surface region of the ink, leaving the lower ink regions in the container unmoved.
A further disadvantage of the known machine is that after cleaning of the spreader and the spreader support, the precise position on the carriage must be reestablished and fixed, which must be done extremely carefully and precisely and is therefore expensive in terms of time.